Micturition Reflex - Diagram and Process: Definition, Steps, Phases, Disorders

What Is the Micturition Reflex?

The micturition reflex simply known as the reading reflex is a phylogenic activity of an organism that is important in the body's process of eliminating urine from the bladder. The micturition reflex is initiated by the stretching of the receptors in the thickness of the bladder wall, from the filling of approximately 300-400 mL of urine inside the bladder. The micturition reflex involves a complicated neuro-muscular interaction involving the nervous system with the muscles of the bladder and that of the urethra, culminating in the expulsion of urine from the body.

Latest: NEET 2024 Paper Analysis and Answer Key 

Don't Miss: Most scoring concepts for NEET | NEET papers with solutions

New: NEET Syllabus 2025 for Physics, Chemistry, Biology

NEET Important PYQ & Solutions: Physics | Chemistry | Biology

This Story also Contains

1. What Is the Micturition Reflex?
2. Overview Of The Micturition Reflex
3. Stages Of Micturition
4. Labeled Diagram On The Micturition Reflex
5. The Micturition Reflex Process
6. Micturition Reflex
7. Afferent Impulses To The Spinal Cord
8. Efferent Impulses To The Bladder
9. The Detrusor Muscle Contracts
10. Relaxation Of The Internal Urethral Sphincter
11. Receptors Are Stimulated
12. Inhibition Of The Pudendal Nerve
13. Relaxation Of The External Sphincter
14. Self-Regenerative Nature Of The Reflex
15. Disorders Associated With Micturition
16. Diagnostic Tools And Tests
17. Treatment And Management
18. Recommended video on Micturition

Overview Of The Micturition Reflex

The section introduces what the micturition reflex is, its importance, and basically how it operates.

Definition: The micturition reflex is the involuntary response; to urination from the bladder.

Significance: The reflex is crucial in matters of balancing the fluid and in avoiding urinary retention that might result in pain and health problems.

Stages Of Micturition

Storage Phase: The urine is stored inside the bladder, and the sphincter muscles are contracted not to let it be released.

Voiding Phase: As the levels inside the bladder rise, the nerves get stimulated, and the message is forwarded to the brain. The brain replies that implies the contract of the bladder. The process is to let the urine start flowing through the urethra.

Labeled Diagram On The Micturition Reflex

Visual Description: It generally includes the bladder, the urethra, the nerves, and the associated muscles that show an interaction in the process of urination.

The Micturition Reflex Process

Micturition is the voiding of urine from the urinary bladder.

Filling Of The Urinary Bladder

It is a condition where the urinary bladder is filled with urine. When there is a filling of urine in the bladder wall of the urinary bladder is stretched.

Stretch Receptors: Stretch receptors in the urinary bladder sense the rise in its volume and form impulses which are transmitted to the nervous system.

Micturition Reflex

At the point of capacity of the bladder, the stretch receptors send afferent impulses through the pelvic nerve into the spinal.

Transmission of Signal: The stimulus in the stretch receptors produces sensory impulses which are transmitted to the central nervous system.

Afferent Impulses To The Spinal Cord

The sensory impulses as a result of the stretch receptors of the bladder travel via the pelvic nerve and reach the sacral region of the spinal cord.

Centre of Integration: The impulses that arrive in the bladder enter an integration centre, which is the spinal cord.

Efferent Impulses To The Bladder

Motor efferent impulses are sent from the spinal cord through the pelvic nerve back to the bladder.

Stimulation of the Detrusor Muscle: The efferent impulses stimulate the detrusor muscle to lead to its contraction.

The Detrusor Muscle Contracts

The contraction of the detrusor muscle increases pressure in the bladder.

Pressure is built: This pressure pushes the urine into the urethra and out of the body.

Relaxation Of The Internal Urethral Sphincter

There is also an opening of the internal urethral sphincter, which has an involuntary type of control.

Opening of the Passage: The relaxation of the involuntary sphincter will form a passage through which urine can flow from the bladder into the urethra.

Receptors Are Stimulated

There shall be a stimulation of the stretch receptors within the urethra when urine flows.

Reinforcement of Reflex: These stretch receptors send further afferent impulses back to the spinal cord, which also serves to reinforce the micturition reflex.

Inhibition Of The Pudendal Nerve

Through the relay in the spinal cord, the sensory stimulus can be transmitted further to the brain to issue commands and concomitantly inhibit signals transmitted by the pudendal nerve.

Relaxation of the External Sphincter: Through this inhibition, it relaxes the external urethral sphincter and releases the urine.

Relaxation Of The External Sphincter

Upon relaxation of the external sphincter, the bladder voids urine through the urethra to the external environment.

Voluntary Control: This can be aided by the voluntary contractions of the musculature of the walls of the abdomen, which increase the intra-abdominal pressure that aids in the micturition.

Self-Regenerative Nature Of The Reflex

The micturition reflex is self-renewable in a way that the initial contraction of the bladder causes greater stimulation of the stretch receptors.

Cycle: This goes on as a continuous process until the bladder has been emptied, and total micturition has been achieved.

Disorders Associated With Micturition

The disorders associated with micturition are:

Urinary Incontinence

Types and Causes: Stress incontinence, urge incontinence, and overflow incontinence

Treatment Options Available: Behavioural therapy, medications, surgery

Urinary Retention

Causes and symptoms: Blockages, problems with nerves, weak bladder muscles.

Options Available for Treatment: Catheterization, drugs, surgery.

Overactive Bladder

Symptoms and how to manage it: More frequency and urgency, can be managed with drugs and behavioural therapy.

Diagnostic Tools And Tests

Routine Urinalysis: Various tests that analyze the characteristics of urine.

Urodynamic Studies: Several tests that study the functions of the bladder and urethra.

Imaging Techniques: Ultrasound, MRI, and CT scans of the urinary tract.

Treatment And Management

Treatment Of the disorders related to micturition include:

Behavioral Therapies

Bladder Training: Techniques for increasing the storage capacity of the bladder.

Pelvic Floor Exercises: Exercises for increasing muscle power of the urination-controlling muscles.

Pharmaceuticals

Medications: Drugs typically used in the prescription of micturition disorders and their mechanisms.

Surgical Interventions

Procedures: Indications, success rates, and risks included in the various surgical interventions.

Conclusion

The micturition reflex is a very important physiological process by which the excretion of urine occurring from the process of the urinary bladder remains under proper control. Proper knowledge regarding this reflex can be important for the examination of the normal functions regarding urination and ascertaining the possible disorders or problems associated with the process of urination.

Recommended video on Micturition